Author(s): Bui Thi Khanh Chi; Yuji Toda; Tetsuro Tsu Jimoto
Linked Author(s): Yuji Toda
Keywords: Nitrate; Active/passive uptake; Leaf/root nitrogen content; Phragmites japonic
Abstract: It has been reported that the number of bare bar transformed to vegetated bar has been increasing gradually o n Japanese sand-bed rivers in recent decades. Plants require nitrogen (N) and water within the soil to survive and develop. Riparian vegetation, however, is commonly found on sandbar with low mo isture, extremely low subsurface water levels and at a considerab le distance from the river edge which suggests limited access to water and nutrients. In order to thrive on these limiting conditions, it is supposed that plants may possess a specific uptake in their roo t cells. It is a fact that both the transport of nutrients from roo t medium to plant and the relationship of plant nitrogen tissue to nitrogen uptake have not been identified so far. The experiments in this stud y were performed in the summer of 2005 and 2006 in order to define the nitrate uptake and the interrelation of p lant nu trient content to nitrate up take in Phragmites japon ica (P. japon ica). The results suggest that the mayor part of nitrogen absorp tion is due to an active up take process. The diurnal variation in NO3 - up take, root and leaf N content are present. The NO3 - influx is positively correlated to the leaf N content and negatively associated to N content of root. The most interesting feature is the results show the fact that roots have the capability to store nu trient absorbed in nigh time while depleting reserved nutrient supply for leaf demand in daytime.
Year: 2007